I will reiterate a point that was made previously.
Right or wrong, for better or for worse, Tony George made it possible for me, and many, many others I suspect, to have the privilege and honor to watch Billy Boat, Steve Kinser, Donnie Beechler, Jack Hewitt and Jimmy Kite race in the Indy 500.
None of us have any way of knowing what would have happened if Tony George had not done what he did but it's a good bet that we wouldn't have had the pleasure of seeing the aforementioned drivers compete in the Indy 500.
Given NASCAR's exploding popularity during that period of history it's a safe assumption that interest in Indy Car racing was going to tank to some significant extent despite the split.
As far as this F1 guy racing at Indy, good for him and it's probably in some small way good for the 500. You want to see some real excitement? Just announce that Rico Abreu, Christopher Bell and Kyle Larson have rides for the Indy 500. Now that would heighten interest a whole bunch.